Summary of Significant Accounting Policies (Intangible Assets) (Details) (Favorable Lease Rates)	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Favorable lease rates, original useful lives	35 years 10 months 24 days	36 years 4 months 24 days
Minimum
Finite-Lived Intangible Assets [Line Items]
Favorable lease rates, original useful lives	41 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Favorable lease rates, original useful lives	52 years